World leader expressed shock and sadness at the incredible violence that rocked Paris Friday night.
German Chancellor Angela Merkel said she is "deeply shaken by the news and pictures that are reaching us from Paris."
The German leader issued a statement saying her thoughts were with the victims "of the apparent terrorist attack."
The Secretary-General of the NATO alliance says he is "deeply shocked by horrific Paris attacks."
Jens Stoltenberg said in a Twitter message that "We stand together with the people of #France. Terrorism will never defeat democracy."
Related: At Least 100 Dead in Multiple Paris Terror Attacks
U.N. Secretary-General Ban Ki-moon is condemning "the despicable terrorist attacks" in Paris and is demanding the immediate release of numerous hostages being held in the Bataclan theater.
President Barack Obama is calling the attacks on Paris "outrageous attempt to terrorize innocent civilians" and is vowing to do whatever it takes to help bring the perpetrators to justice.
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Speaking to reporters at the White House, Obama said he would not speculate about who was responsible.
He called the attacks a "heartbreaking situation" and an "attack on all of humanity."
Obama was briefed on the attacks Friday by his counterterrorism adviser Lisa Monaco.
He said that the U.S. would stand with France in the face of the attacks.
"We're going to do whatever it takes ... to bring these terrorists to justice," he said.
Obama later called French President Francois Hollande to offer the condolences of the American people, the White House said a statement Friday night
"The president reiterated the United States' steadfast, unwavering support for the people of France, our oldest ally and friend, and reaffirmed the offer of any necessary support to the French investigation," the statement said.
U.S. Secretary of State John Kerry, in a separate release, added, "I share President Obama's outrage and sadness over the terrorist attacks tonight in Paris ... These are heinous, evil, vile acts. Those of us who can must do everything in our power to fight back against what can only be considered an assault on our common humanity."
British Prime Minister David Cameron said he was "shocked" by the brazen attacks.
Cameron said on Twitter "Our thoughts and prayers are with the French people. We will do whatever we can to help."
And at the Vatican, Fr. Federico Lombardi, a spokesman for Pope Francis, said, "We are shocked by this new manifestation of maddening, terrorist violence and hatred which we condemn in the most radical way together with the Pope and all those who love peace. We pray for the victims and the wounded, and for all the French people."
Israeli Prime Minister Bejamin Netanyahu said: "Israel stands shoulder to shoulder with French President Francois Hollande and with the people of France in our common battle against terrorism."
The attacks, which left at least 120 dead, came as the French president is preparing for two trips abroad. He's slated to leave Saturday for a nine-day trip to Turkey, the Philippines and Malaysia. He's due to travel to Paris for climate change talks at the end of the month.
Immediately following the series of attacks, Hollande said he was closing the country's borders and declaring a state of emergency after several dozen people were killed in a series of unprecedented terrorist attacks.
Hollande, in a televised address to his nation, said the nation would stand firm and united against the attackers.
He said security forces are assaulting one of the sites hit by Friday's attacks, without elaborating.
"It's a horror," he said.